UCR Entomology Bees

Agricultural Impact of Africanized Honey Bees in Sinaloa, Mexico

(This article appeared in slightly different form in California Agriculture 50:24-28 1996)
Francis Ratnieks and P. Kirk Visscher Department of Entomology
University of California, Riverside, CA 92521, USA

Abstract

In Sinaloa, Mexico, there is large scale agriculture similar to California's, and there are well established Africanized honey bees . Beekeepers have adapted their management practices to continue to provide pollination of crops. Similar adjustments as Africanized bees become established in California can probably maintain effective honey bee pollination of California crops.

(Image above) Honey bee hives in place for pollination of squash. These bees are kept in extra-large hive bodies, about equivalent to pollination units in California.

Introduction

Africanized honey bees have recently arrived in California. They were first detected in the fall of 1994, near Blythe. As of April 1996 there have been 21 colonies identified as Africanized, mostly in Imperial County. These newcomers are worrisome both for California beekeepers and for growers who rely on honey bees for crop pollination. California crops requiring bee pollination include almond, avocado, plum, prune, cherry, apple and other tree crops, cucumbers, melons, squash, alfalfa, vegetable seeds, kiwi fruit etc. The annual value of these crops is several billion dollars. To ensure adequate pollination, about 1.4 million hive rentals occur each year in California, accounting for approximately half of all US rentals.. About half of the pollination rentals in California are in almonds alone.

The extent to which California will be colonized by Africanized bees, and the extent to which managed bee hives will be affected is unknown. However, it is safe to say that in areas that do become colonized with Africanized bees some changes in apicultural and agricultural practices will be necessary, and that there will be a period of a few years in which beekeepers, growers, and the public adjust to the new situation.

One way of hastening any adjustment process is to take advantage of knowledge acquired by beekeepers and growers in Mexico, where Africanized bees have been present for nearly ten years. Accordingly, we visited beekeepers south of the border to see what was occurring there. To collect information as useful as possible to California growers and beekeepers, we went to Sinaloa, a part of Mexico where beekeepers derive most of their income from pollination rentals, as in California, and where the agricultural system is similar to California's agricultural valleys. In contrast, in most of Mexico, as in most of the US, the main income for beekeepers is through honey sales. Our visits were in January 1995 and December 1991. During these visits we visited apiaries and farms where hives were being rented, and spoke with beekeepers, and department of agriculture officials.

The information we present below shows that bee pollination of crops can continue in an area that has been fully colonized by Africanized bees. Hopefully, California will not be extensively colonized by these bees. However, even if California is extensively colonized the information we have collected suggests that agriculture need not be greatly affected.

Agriculture in Sinaloa

Background

The state of Sinaloa lies on the west coast of Mexico, beside the Pacific ocean and the Gulf of California. The Western Sierra Madre mountain range forms the eastern boundary. The state extends about 200 miles north and 100 south of the Tropic of Cancer. The main agricultural area is the flat coastal plain, about 200 by 40 miles, in the northern two thirds of the state, from Culiacan to Los Mochis. This zone is connected by about 550 miles of four lane highway to Nogales, Arizona, the main entry point for its exports to the US. The Sinaloa climate is tropical and dry, with three rainy months in our summer. Numerous dams in the mountains store irrigation water.

Crops

In appearance, the Sinaloa coastal plain is similar to California's Central Valley. In both areas crops are grown near sea level under irrigation in large fields using mechanized methods. In contrast to the Central valley, row crops are grown all year round and there are fewer tree crops or vines.

During the US winter, Sinaloa provides many of the fresh vegetables we eat, particularly tomatoes, cucumbers, squash, eggplant, and peppers. In addition, numerous other crops are grown, such as corn, wheat, beans, garbanzos, sesame, cardamom, mango, avocado, citrus, banana.

The large scale of agriculture in Sinaloa is illustrated by reference in the local paper to about 500 truck loads of vegetables crossing the US border in Nogales each day during the time of our visit in January. Culiacan popular baseball team is called the Tomateros (Tomato growers), attesting to the importance of the importance of agriculture to the Sinaloa economy.

Pollination needs

Because of intensive agriculture, many crops in Sinaloa, as in California, require growers to rent bee hives to ensure pollination. Without adequate pollination, yields are reduced, and the vegetables may be too small or misshapen for the US market. Cucumbers account for 90% of all hive rentals. The introduction of hybrid cucumbers with few male flowers has resulted in an increase in the optimum hive density from 3 to 6 per hectare on farms with progressive managers (one hectare = 2.5 acres). Additional crops for which hives are rented are various squashes, melons, and eggplant. In all these crops 3-6 hives per hectare are used, depending on the grower. Each year there are about 30,000 hive rentals (some hives are rented more than once). About half of these rentals were supplied by Mr. Javier Pompa, one of the beekeepers we visited and the president of the state beekeepers association. The rental fee for the last few years has been 80 new pesos, or $23 (exchange rate prior to recent devaluation of the peso). Rentals last 30-40 days, except for eggplant which lasts twice as long and is considered to be two rentals in calculating the fee. Growers use large amounts of pesticides, often resulting in bee kill. Much of the pesticide damage comes from daytime spraying with tractors and by hand. Beekeepers are not compensated for these kills, nor for the theft of hives. However, they are compensated if hives are damaged by farm machinery.

Africanized honey bees

History in Sinaloa

The Africanized honey bee arrived in Sinaloa around 1990. In December 1991, Mr. Pompa told us the Africanized bees had not yet had an impact on beekeeping, because most colonies still had their original European queens. The impact of Africanization was felt over the next few years as the hives managed by beekeepers became, to a greater or lesser extent, Africanized.

The Africanization process in Sinaloa was dramatic, with vast numbers of swarms invading the area. As an indication of the number of swarms arriving, approximately 1700 swarms and feral colonies were eliminated by public authorities in the city of Culiacan, population ca. 500,000, during 1994, according to a SARH official. One church had over 40 feral colonies. As another indication, a beekeeper near the small town of San Ignacio with five apiaries paid a bounty for the elimination of feral nests in his area, resulting in 650 feral nests being located within a few miles of his apiaries.

As in other parts of Latin America, the Africanized bee has lived up to its other name of killer bee, with 18 fatalities so far in Sinaloa, according to a SARH official. Most of the victims were elderly, and thus unable to run out of danger and in many cases were killed by less than one hundred stings, a number which would be painful but not life-threatening to a younger adult. It is important to note that all of these deaths were caused by feral colonies or possibly swarms. None were caused by bees managed by beekeepers.

Economic effect on beekeepers

Beekeepers have been economically affected by the arrival of the Africanized honey bee but have not been put out of business. The three main costs to beekeepers have been:

(1) Reduction in the honey yield of their colonies. The causes are unknown, but probably are a combination of increased competition with feral colonies for nectar resources and the tendency for Africanized bees to invest more in rearing brood than storing honey. (Mr. Javier Pompa's honey crop has reduced from 400 to 100 barrels per year due to less production per hive and a reduction in the total number of his hives from 10,000 to 7,000. Mr. Manuel Sosa's crop per hive has reduced from 40kg to 25kg; 1kg = 2.2lb.)

(2) Reduction in the total number of hives kept, because many colonies absconded (the entire colony left the hive) after they became more or less Africanized. Absconding is rare in European bees but common in Africanized bees, in response to disturbance or shortage of forage. Beekeepers in Sinaloa replace colonies that abscond by dividing hives and capturing swarms, but they are still not back up to their original hive numbers.

(3) Payment of higher wages. Mexican beekeeping is more labor intensive than in the US with one employee per 300-500 hives. Mr Pompa, for example, has not had to employ more people but has to pay higher wages to compensate for more difficult working conditions (wearing heavy bee suits in a hot climate, more stings, more night work). Currently Mr. Pompa pays his employees 35 pesos per day, over twice the minimum wage, equivalent to $1.25 per hour at pre-devaluation rates.

However, the arrival of the Africanized bee has hardly affected Mr. Pompa's income from pollination rental, because he has been able to provide sufficient colonies of hybrid bees to fulfill his contracts. On the plus side, Mr. Pompa and Mr. Sosa report that the hybrid bees they now use are less affected by brood diseases such as American and European foulbrood and are less subject to theft.

(Image above) These colonies in a large cucumber field are hybrids: their queens are European, but have mated with Africanized drones. They are more defensive than similar European colonies, but not as fierce as Africanized colonies. Even while the hives were being opened, here, workers were able to work nearby.

Changes in beekeeping practices

In order to keep and manage bees, Sinaloa beekeepers have adopted the new management practices recommended for managing Africanized bees, as follows:

• Use of bee suits and gloves when managing colonies.
• Moving hives at night when relocation is necessary.
• Relocating any apiaries previously close to buildings or roads. A minimum distance of 200 meters is recommended by the Mexican department of agriculture (SARH) and greater distances are preferred.
• Feeding syrup to colonies when forage conditions are poor to discourage absconding.
• Queen rearing to ensure manageable stock.

Queen rearing is probably the key innovation. Mr. Sosa, Mr. Pompa, and the other beekeepers we visited now have queen rearing operations, and stated that a beekeeper has to be a queen rearer. They estimate that it is necessary to rear about one new queen per year per hive managed. Queen rearing enables beekeepers to use colonies headed by a pure European queen, mated to local drones. As a result, the worker bees, who are the offspring of the queen and her mates, are a mixture of pure European bees and hybrids. Because honey bee queens mate with 10-20 males, each colony probably contains a mixture of both types of workers. Approximately two thirds of the colonies headed by these queens are reasonably "gentle" (though not as gentle as most pure European colonies). One third are manageable but exhibit undesirable Africanized bee qualities (excessive defensiveness, excessive brood rearing at the expense of honey storage). These can be identified during routine hive management and given a replacement queen that the beekeeper has reared. Queens can be reared year-round in Sinaloa, unlike most of the US. Queens are marked with a small spot of paint on the thorax, so that natural queen replacement can be detected, since this will give rise to colonies that are genetically more strongly Africanized.

Queens can be purchased in Mexico, but are relatively expensive ($4-$5), making it worthwhile for beekeepers to rear their own. In addition, rearing queens enables the beekeeper to be sure of quality. Breeder queens (i.e., pure European queens mated to all European drones) from which to rear virgin European queens for local mating are available from queen rearers in La Paz, Southern Baja California (a state which has not yet been Africanized); from a department-of-agriculture(SARH) run breeding station on the Islas Marias, a group of islands about 70 miles from the coast; and from Hawaii. (Other US sources are currently precluded because Varroa mites, a serious parasite of honey bees, are not yet found in Sinaloa. They are found throughout much of Mexico, and all the US except Hawaii.)

(Image above) Feral Africanized bee colonies had made nests in each of the windows visible in this hospital building. These unmanaged Africanized bees do pose a threat, and there have been stinging deaths.

Social background

In Mexico, beekeepers are fortunate to be working within a social framework in which they can continue to go about their business without being tied down by regulations. Numerous authorities and organizations (the department of agriculture, red cross, schools, the fire brigade, police) combine to promote public awareness about the realities and dangers of Africanized bees, and also to eliminate dangerously located colonies of feral bees within the cities. Liability problems seem much lower in Mexico than in the US. As mentioned above, hives managed by beekeepers have not been responsible for any of the deaths due to Africanized bees in Sinaloa.

Management of pollination units

Growers have been completely unaffected by Africanization, because beekeepers have been able to supply sufficient colonies for pollination. In addition, there have been no deaths or serious incidents caused by pollination hives. In fact, the beekeepers have been so successful in adapting to the arrival of Africanized bees that most growers are unaware that the bees currently pollinating their crops are any different than five years ago.

The success of the beekeepers in adapting has several angles. The most important is that beekeepers maintain less defensive bees in their hives by requeening with locally mated European queens. Also of importance is that colonies are moved into the fields and unloaded at night, typically after being loaded in the late afternoon or evening. This gives the hive time to calm down before daylight. If a colony is unloaded in the daytime, as was formerly common, the bees are more likely to abscond and are highly defensive. Even when moved at night, colonies remain more defensive than normal for a day or so after moving.

Pollination hives are set out in the crops in groups of about 10 (or whatever the grower wants) along or close to farm roads going through or around the crop, similar to California practices. The hives are located exactly as before Africanization, with no attempt to segregate people and hives. We observed large numbers of people working and eating lunch within 20 yards of hives, and walking right by them. Occasionally, someone is stung and carries on working. Farm workers know to avoid colonies recently moved into the fields.

Another factor that probably reduces the defensive behavior of the bees is the use of pollination hives with relatively low numbers of bees, comparable in number of bees to hives used in almond pollination in California. Hives used to pollinate almonds contain relatively few bees because almond bloom occurs in February, before colony populations have had time to expand following the winter. In contrast, the Sinaloa hives are weak by choice of the beekeepers.

Hives used for pollination consist of a single jumbo hive body containing about seven frames, with no additional honey-storage boxes. This is a comb area equivalent to 9 frames in a deep hive body commonly used in the U.S. Bees cover most of these frames. (For almond pollination, most hives are rented in two deep boxes, giving twice the comb area used in Sinaloa, but approximately the same number of bees.) Normally, a jumbo hive box holds nine or ten frames, so there is a space in the hive when only seven frames are used. Cans for feeding syrup are placed in this space and filled as necessary to provide the bees with food. Generally speaking, the bees do not do well during pollination because of a shortage of forage and the loss of foraging bees due to pesticides.

The use of a single jumbo hive box as brood chamber is standard in northern Mexico, and predates the arrival of Africanized bees. Relatively small pollination units without honey supers were originally used for the following reasons:

• Easier to load by hand onto trucks.
• Can be closed when insecticides are sprayed with wire mesh over the entrance with little danger of suffocation. More bees in the hive increases the suffocation danger.
• No danger of frames of honey melting or breaking during transit, leading to a sticky mess and the death of the hive.
• Because farm workers often kill hives to steal a frame of honey, the use of small hives minimizes this loss. (With the advent of Africanized bees and the use of hybrid colonies for pollination theft of honey has decreased. Theft of hives is seldom a problem in California.).
• More income for the beekeeper from a given amount of bees and equipment.

Fortunately, these relatively small pollination units have proved ideal in the post-Africanization period. About the only difference following Africanization, is that growers are no longer willing to set the entrance screens used to protect the hives from pesticide application. This would seldom be a problem in California, because pesticides are applied more carefully with regard to the health of pollinating bee hives and beekeepers rarely close up their hives to protect them.

Conclusion regarding pollination

The arrival of Africanized bees in Sinaloa has not had a great impact on commercial pollination, and has affected predominantly the beekeepers. For the grower, there has been no rise in the rental fee or shortage of pollination units available. This is because the beekeepers have been able to adapt their management practices. Although beekeepers lost hives following Africanization they were able to divide hives and rear queens to make up the numbers, although they are still not up to pre-Africanization numbers. From the perspective of the beekeepers, pollination contracts have probably helped them to survive economically, because honey production has reduced considerably following the arrival of Africanized bees.

How relevant are these Mexican experiences for California? We think that they are a cause for some optimism. If Africanized bees should colonize much of California, which is by no means certain, and probably unlikely, the Sinaloa situation indicates that beekeepers will still be able to supply the necessary bees for crop pollination. In one key respect California is better off than Sinaloa because queen rearing is already highly developed here, and California queen rearers have the capacity to rear large numbers of replacement queens if needed, including European queens mated to European drones. (The major queen rearing areas are in the Sacramento valley, hopefully further north than colonization will reach.) On the other hand, the total requirement of growers in California for hive rentals is about 50 times greater than in Sinaloa and cannot be met by in-state beekeepers alone. In particular, almond pollination will be greatly affected if regulations regarding Africanized bees limit the movement of bees between California and other states. Perhaps the biggest lesson from Sinaloa is that if beekeeping is profitable, and if beekeepers are allowed to continue their trade and are assisted in adapting to the new bees, then they will be able to supply the bees needed for pollination. Growers can support beekeepers, and themselves, by pushing for a rational reaction to Africanized bees if they arrive in large numbers, (i.e., one that recognizes that bees are necessary for pollination and that most of the public health problem of Africanized bees is not caused by managed colonies) and by making sure that beekeeping remains profitable.